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n. UCR (under color removal) Processing
Theoretically, mixing Y, M,'and C toners in
equal parts should produce black. However, since
neither one of the toners has pure color absorp-
tion characteristics*, mixing the three toners rep-
resenting three colors will not produce pure black.
In this block, the Bk signal is generated based
on the Y, M, and C signals so that the reproduc-
tion of black can be improved by the addition of
the Bk signal to the Y, M, and C signals.
See discussions on YMC conversion.
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The Bk signal is generated as follows:
The gray components of the YMC signals are
as indicated in Figure 3-333.
These gray components are removed and
replaced with the Bk signal. The replacing com-
ponent used here is called an UCR amount, and
in the case of Figure 3-334, the UCR amount is
100%. In such a case, Bk toner will be added to
all density areas, possibly causing fogging in light
areas.
As a remedy, the UCR amount is increased or
decreased with reference to the text signal, there-
by limiting the UCR amount to less than 100%.
This processing is executed for each pixel.
CANON CLClOOO REV.1 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
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Y
Gray component
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Figure 3-333
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Figure 3-334
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UCR
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Figure 3-335
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